This invention relates to a time-lag fuse using several fine ceramic sintered bodies which are porous or superior in heat conduction as arc extinction material.
A fuse filled with arc extinction material to elevate the breaking capacity is defective in that, due to irregularities in grain distribution of the arc extinction material, the filling rate varies so that the fuse characteristics are hard to stabilize. And a current-limiting fuse using a porous ceramic sintered body as arc extinction material to eleminate such irregularities in grain distribution is publicly known, but this type of fuse poses problems such that, because of its construction in which the fuse element and the ceramic sintered body are contacted with each other directly, the heat transfer from the fuse element to the ceramic sintered body is great, that, due to such heat transfer, the thermal balance of the fuse element varies so that the time-lag characteristic of the fuse element lowers and, at the same time, the ceramic sintered body and the insulating cylinder strikingly rise in temperature, that, in the case where a spirally wound fuse element is placed inside the ceramic sintered body, it is difficult to contact the fuse element and the ceramic sintered body with each other uniformly over the lengths thereof, so that the fusing characteristic of the fuse is hard to stabilize, and so forth.